1498 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1957 



verted into digital representation by means of an electronic stop-watch 

 (time encoder). 



4.2 Vernier Follow-up System 



A vernier follow-up system can be built much like the present two 

 speed synchro control-transformer system, except that the geared up 

 synchros are replaced by vernier resolvers. Fig. 9 illustrates the vernier 

 portion of this system. Since the output impedance of the vernier re- 

 solver is fairly large, it may be desirable to use amplifiers, as shown in 

 Fig. 9, to energize that vernier resolver which plays the part of the con- 

 trol-transformer. 



4.3 Vernier Angle-Reading System 



A visual vernier angle-reading system as reciuired to read the position 

 of a rotary table can be built by using the output of a vernier resolver 

 to position a standard resolver. 



The coarse angle can be read as usual from calibration lines marked 

 directly on the rotary table. The vernier angle reading is obtained by 

 coupling a vernier resolver directly to the rotary table. The output of 

 this resolver is used to position a standard control transformer. This 

 control transformer will go through "w" revolutions for each revolution 

 of the rotary table, where "w" is the order of the vernier resolver. The 

 reading of a dial coupled either directly or through gears to the control 

 transformer provides the vernier reading. 



V. SUMMARY 



Vernier resolvers of order 26, 27, 32 and 33 have been designed, built 

 and tested. 



The construction of the unit is very simple because all windings are 

 located on the stator. The absence of brushes and slip rings makes the 

 unit inexpensive in production and reliable in performance. 



The performance of present experimental models is characterized by 

 a repeatability of better than ±3 seconds of arc and by a standard de- 

 viation error over one revolution of less than 10 seconds of arc. 



Production units should be of even higher accuracy because better 

 tooling fixtures would be used and minor design improvements would be 

 incorporated. 



The principal forseeable application of the resolver lies in vernier sys- 

 tems. Vernier encoder, vernier servo and vernier angle-reading systems 



